COMEDK 2025 Evening Solved Paper

Concept:Bond angles depend on molecular geometry and lone pair repulsion.Explanation:First, find the geometry and bond angles for each molecule.$\mathrm{XeF}_2$ is linear, with an $\mathrm{F-Xe-F}$ angle of $180^\circ$.$\mathrm{BF}_3$ is trigonal planar, with an $\mathrm{F-B-F}$ angle of $120^\circ$.$\mathrm{NH}_3$ is trigonal pyramidal, with an $\mathrm{H-N-H}$ angle of about $107.5^\circ$ due to one lone pair.$\mathrm{PF}_3$ is also trigonal pyramidal, but the $\mathrm{F-P-F}$ angle is smaller, around $98^\circ$, because phosphorus is larger and lone pair repulsion is more pronounced.Arranging in decreasing order of bond angles: $180^\circ > 120^\circ > 107.5^\circ > 98^\circ$.Therefore, the order is $\mathrm{XeF}_2 > \mathrm{BF}_3 > \mathrm{NH}_3 > \mathrm{PF}_3$.Answer:Option B: $\mathrm{XeF}_2 > \mathrm{BF}_3 > \mathrm{NH}_3 > \mathrm{PF}_3$